The present invention is directed to methods and apparatus for directing a beam towards a receiving device (e.g., beam-forming), and more particularly to performing beam-forming in the presence of interference.
Beam-forming is a signal processing technique used in systems for directional signal transmission or reception. The spatial selectivity may be achieved by using adaptive or fixed receive/transmit beam patterns. Beam-forming takes advantage of constructive/destructive wave interference to change the direction of the beam. As defined herein, a beam is the electromagnetic wave, carrying data to a receiver, which is formed by the (constructive/destructive) interference pattern of two or more waves transmitted by one or more antennas.
Typically, when shaping the beam, interferences caused by noise and/or other signals transmitted by other sources are disregarded. This is because beam-forming is traditionally performed in environments with only one transmission source (e.g., WiFi systems). In particular, in such environments, signals transmitted to different users are separated into different time slots avoiding the need to compensate for any other interferences. Additionally, receiving devices in such environments communicate with the single transmission source and no other source.
However, more complex systems (e.g., cellular, WiMAX and 3GPP Long Term Evolution (LTE) systems) may use multiple transmission sources (i.e., base stations) to communicate with a receiving device (i.e., mobile station). Thus, it becomes more difficult to shape a beam at a particular transmission source using known techniques as interferences caused by the other transmission sources alter the intended shape of the beam.